Generally, an internal combustion engine, particularly an engine of 4 stroke cycles, generates driving torque through intake, compression, expansion, and exhaust strokes in each combustion chamber. Such an engine changes heat energy generated from fuel combustion into kinetic energy.
In this case, the combustion chamber of the engine is formed by combining a cylinder head with a cylinder block, and a piston is installed in the cylinder block to reciprocate so that the volume of the combustion chamber may be varied according to a reciprocating motion of the piston associated with the compression and expansion strokes.
The cylinder head is provided with an intake port for introducing air into the combustion chamber and an exhaust port for emitting an exhaust gas combusted in the combustion chamber, an intake valve for opening and closing the intake port and an exhaust valve for opening and closing the exhaust port.
The cylinder head is provided with an injector which injects fuel into the combustion chamber and is installed to be adjacent to the intake port, and a spark plug for igniting the fuel injected by the injector.
Recently, a gasoline direct injection (GDI) engine which directly injects gasoline fuel into the combustion chamber has been researched and used, and the gasoline direct injection engine operates with a lean air/fuel ratio, thereby reducing fuel consumption, improving intake efficiency and increasing power.
The gasoline direct injection engine may produce a higher compression ratio than a typical gasoline engine, and may effectively maximize power generated.
However, in the gasoline direct injection engine, fuel particles of gasoline injected into the combustion chamber are adsorbed to an inner wall of the combustion chamber, the piston, and the spark plug and are not completely combusted, resulting in abnormal combustion.
Moreover, due to the adsorption of the fuel particles, the combustion chamber, the piston, and the spark plug may be damaged, a carbon stack may occur, and a starting delay and thus additional fuel injection may occur, such that a durability of the engine and fuel efficiency may deteriorate.
The above information disclosed in this Background section is only to enhance the understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.